public class Test2 {
        public static int mySqrt(int x) {
            if(x<1) return 0;
            long left=0,right=x;
            while(left<right){
                long mid=left+(right-left+1)/2;
                if(mid*mid<=x){
                    left=mid;
                }else{
                    right=mid-1;
                }
            }
            return (int)left;
        }
}
